Desertification: The Gradual transformation of habitable land into deserts; usually caused by climate change or by destructive use of the land also, the definition of desertification is:
"The transformation of arable or habitable land to desert, as by a change in climate or destructive land use."
Desertification affects many nations. China, South Africa and the US are some of the worst affected.
Any habitable land that has been turned into a desert due to the climate or human activity.